setting up the xy hub index page + adding an announcement

used the old ou hub css as a base, changed some aspects (color, added border radius) and fixed poor elements of the code for a new design. announcement covers the quick ban of blaziken and deoxys-n.
Merge pull request #136 from smogon/e4e93c3618bb46a949e2bd41d8916a66

setting up the xy hub index page + adding an announcement